This invention relates to a linkage mechanism for an implement, such as a bucket, dipper or the like.
In material handling apparatus such as mobile power crane-excavators, a load carrying member such as a boom is provided with an outer end to which is pivoted a saddle block. A translatable stick passes through the saddle block and is movable by a stick cylinder ram. A material handling implement is pivotally attached to the outer end of the stick. An implement cylinder is mounted to the assembly to pivot the implement on the stick for digging, dumping and the like.
In some instances, as with a bucket which digs or crowds forwardly into the ground and then must lift its load for subsequent transport and dumping, the implement cylinder must provide a so-called "breakout force" in order to move through the material being dug.
Heretofore, the capacity of the implement cylinder sometime had to be increased for the purpose of providing additional breakout force. Heretofore, this increased capacity was achievable only with a larger implement cylinder and consequent greater power demand. Furthermore, prior constructions were such that the speed of implement roll was solely dependent on the speed of action of the implement cylinder.
It is the aim of the present invention to provide a construction to augment the normal force moment of roll about the implement pivot axis with an additional moment created by structure other than the implement cylinder; thus reducing the need for an oversized capacity implement cylinder.
It is a further aim of the invention to augment the position of the digging implement during pivoting thereof to thereby increase its speed of operation.
An additional aim is to provide a device accomplishing the above aims which nevertheless permits the implement cylinder ram to pivot the digging implement even when the stick cylinder ram is fixed in length.
In accordance with one aspect of the invention, the ram of the stick cylinder is utilized to augment the force moment of the digging implement about its pivot axis, thus supplementing the force moment created by the ram of the implement cylinder. The total force moment is thereby increased.
In the present embodiment, the ends of the stick and implement cylinder rams are connected to common lever arms which are pivoted to the stick on a transverse axis which is offset from the ram-lever connections and from the stick center line. The lever arms are connected to the digging implement in a manner so that the combined forces from both rams are transmitted to the implement to pivot the latter about its axis. In this embodiment, the stick cylinder ram is not connected to the stick directly, but rather through the lever arms.
In accordance with another aspect of the invention, the augmentation of force moment automatically augments the positioning of the digging implement in that the pivot axis of the implement simultaneously shifts forwardly or rearwardly, thus changing the speed of implement rotation during loading or dumping. In the present embodiment, the simultaneous movement of the stick cylinder ram and the implement cylinder ram causes the stick to extend or retract, thus causing a shift of the implement pivot axis relative to the saddle. A forward-and-roll or rearward-and-roll effect is thereby created, giving the operator increased flexibility in moving the implement.
In accordance with yet another aspect of the invention, the implement may be pivoted even when the stick ram is fixed in length.
In the present embodiment, the pivot axis between the stick cylinder ram and levers, while selectively not shiftable longitudinally, is movable vertically to accommodate lever and implement pivoting.